Biomedical subjects
Publications and source records attributed to E A McGlumphy.
Osseointegrated implant support of dental restorations continues to be a popular option for the contemporary patient with missing natural dentition. This article focuses on the two most frequently used methods for attaching final prostheses to endosseous implants. The authors offer practical solutions for minimizing implant screw loosening and describe the factors involved in maintaining stable screw joint assembly.
A special interest group meeting devoted to clinical educational programs in implant dentistry for undergraduate students was held in March 1994 at the annual session of the American Association of Dental Schools in Seattle, Washington. Summaries of the presentations of representatives from three United States dental schools and the moderator's introductory remarks are included in this article.
This article describes the process of making and using a surgical guide stent. It is intended to enable the surgeon to maintain the same horizontal and vertical axes of cylindrical endosseous implants during the surgical phase of implant placement as those determined at the treatment planning stage. Furthermore, the stent can be used with the entire series of surgical drills, thereby minimizing the chance of inadvertently enlarging the implant site as a result of freehand use of the handpiece.
This study was conducted to determine the effect of abutment angulation on the stress field near a specific dental implant. Photoelastic resin was cast directly to five 3.8 x 10-mm Steri-Oss implants in 50 x 70 x 13-mm molds. One additional model was fabricated with a strain gauge rosette embedded in the resin to allow precise determination of normal stresses. Zero-degree, 15-degree, and 20-degree abutments were assembled on each of the six implants, subjected to 178 N load, and viewed with a circular polariscope. Observed fringe patterns were photographed for all six models, and strain indicator readings were recorded for the strain gauge model. Numerical data from the strain gauges produced results that agreed with the visual interpretation of the isochromatic fringes. Strain gauge data were also used to calculate the principal stresses and strains. Although a statistically significant increase in stress and strain was found for each increase in abutment angulation, all three abutments produced principal strains that appear to be within the physiologic zone for bone. All values for stress and strain were determined at the location of the rosette, approximately 4 mm from the implant. Higher stresses and strains exist in regions closer to the fixture.
The aesthetic replacement of a single anterior tooth has been revolutionized by the advent of dental implant technology. The learning objective of this article is to enhance the knowledge of single tooth restorations through the discussion of the restorative techniques, soft tissue management, and aesthetic considerations. The techniques presented can be used to obtain predictable results in the anterior region for aesthetic, hygienic, and functional restorations.
Retrievability is the major advantage of screw-retained implant restorations compared to cement retention; however, implant screw loosening continues to be a frequently cited disadvantage of this technique. This paper describes the factors involved in maintaining a stable screw joint assembly by maximizing preload on the retaining screw while minimizing joint-separating forces. Practical clinical solutions to minimize this clinical problem are suggested. Readers are cautioned to address both the occlusal and biomechanical etiologies of screw loosening.
The dental profession has in the past overreacted to anecdotal reports of both positive and negative outcomes involving implants. Because implant complications usually involve multiple variables, it is necessary to isolate these variables as much as possible when structuring a study to assess implant success vs failure. The methodology used in a study of Omniloc implants is reported, including detailed criteria for patient exclusion, patient demographics, statistical method, measurement indices, control procedures, and success criteria.
Because of reported prosthodontic failures, alternative implant abutments and screws with suggested strength superiority have been manufactured. However, little quantitative data are available to support these claims. This study compared the force necessary to cause failure in many of the more commonly used implant and abutment combinations. An 18-mm cantilever test prosthesis was constructed for each system and loaded on an MTS machine until failure occurred (n = 5 for each sample). The mean failure forces ranged from 1.22 to 17.23 kg. The failure force and location of failure for each individual system are reported.
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It has been suggested that there is a unique set of problems associated with joining an implant and a natural tooth with a fixed partial denture. The manufacturer of the IMZ implant system claims that this procedure can be accomplished successfully because of the planned stress-distributing characteristics of their resin internal (intramobile) element. This study compared the difference in the stress patterns generated in photoelastic plastic by an IMZ implant with a resilient or a rigid internal element. Under a standardized cantilever load, the stress patterns were photographed in the field of a circular polariscope. The total stress areas were calculated and a statistical comparison performed. The static load conditions of the model demonstrated no statistical difference between the area of stress pattern generated by an IMZ implant with or without a resilient internal element. Moreover, a single load produced the same deflection of the cantilever beam regardless of which element was interposed.
Although involvement of the jaws by Ewing's sarcoma is uncommon, when it occurs the clinical and radiographic presentation may mimic an inflammatory process, specifically pericoronitis. A case that illustrates this dilemma is presented.
The purpose of this study was to evaluate differences between the occlusal contacts of edentulous patients with mandibular implant-supported hybrid dentures opposing maxillary complete dentures and those of patients with conventional maxillary and mandibular complete dentures. Six parameters related to occlusion were measured in the 2 groups (n = 40 for each group) using pressure-sensitive film. The mean values generated by each test group for each parameter were compared using a t test. Pearson's correlation coefficients between occlusal force, age, and time in function were examined. Occlusal force and area in the implant denture wearers were larger than those in the conventional denture wearers. No significant difference was seen in occlusal force balance between the left and right sides. The center of occlusal load in the implant denture wearers was more anterior. The maxillary denture may become more unstable in implant denture wearers. It is suggested that the stability and retention of a maxillary denture be checked and the occlusion be adjusted more frequently in the hybrid denture wearer than in the conventional denture wearer.
The dislodging force, the compressive strength at 24 hours, and the film thickness of four resin composite luting cements (UDA, UDA with fluoride, Panavia OP, and DenMat) and a conventional glass-ionomer cement (Shofu Type I) were compared. The axial force necessary to dislodge each cemented 0 degree abutment from an internally threaded Steri-Oss implant (n = 5) was then determined using a mechanical testing machine. UDA with fluoride appears to be a significantly stronger luting agent for abutment cementation than is either UDA or DenMat (P less than .05). DenMat resin composite cement exhibited the highest mean compressive strength whereas Panavia OP had the lowest value for film thickness.
The purpose of this study was to investigate the microstructure of plasma-sprayed hydroxyapatite coatings and the elemental composition near the coating-substrate interface for two commercial implants, using the scanning electron microscope. Both coating surfaces and cross-sectioned specimens were examined. The results indicated that while the surface microstructures of both implants were consistent with the plasma-spraying process, the scale of the constituents was much finer for one product. In cross-section, both coatings exhibited minimal porosity and intimate contact with the titanium alloy substrate. It was found that limited interdiffusion of titanium and calcium occurred near the interface.